<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <form id="form">
      姓名: <input type="text" name="name" /> <br />
      年龄: <input type="text" name="age" /> <br />
      头像: <input type="file" name="avatar" /> <br />
      <button id="btn">提交</button>
    </form>
    <script>
      btn.onclick = function (e) {
        e.preventDefault()

        // 获取form的真实dom
        const form = document.getElementById('form')
        // 实例化formdata
        const formdata = new FormData(form)

        const xhr = new XMLHttpRequest()
        xhr.open('post', 'http://localhost:5000/test')
        xhr.send(formdata)
      }
    </script>
  </body>
</html>
